The process to which this invention relates should be distinguished from those processes in which flocking is selectively applied to a substrate to form pattern. In those cases the pattern is usually applied to the substrate in the form of an adhesive and the flocking is then applied to the substrate, where it selectively adheres to the adhesive pattern.
With the inventive process, on the other hand, the flocking is adhered to the entire substrate or an area thereof, with the fibers being given a uniform orientation by means of an electric field, for example. The desired pattern is then impressed by tilting selected portions of the flocking away from that orientation. These portions are visually distinguished from the background patterns by the difference in the orientation of the flocked fibers.
In one prior system for impressing a pattern in flocked material, the material is passed through a nip on one side of which is a heated metallic cylinder whose surface has been embossed with the desired pattern. The raised portions of the cylinder surface heat the flocking fibers contacted by them, thereby, raising the temperature of the fibers above their softening point. Simultaneously, the raised portions bend the fibers over into a new orientation. The fibers are frozen into this orientation upon subsequent cooling and thereby retain the impressed pattern.
The main drawbacks of this prior system are the cost of constructing and operating the heated cylinder, the extended time required to form the cylinder and the need for running the system at elevated temperatures, typically up to 400.degree. F., thereby requiring complex equipment to apply the heat, presenting safety problems and sometimes causing undesired physical changes in the fabric. Moreover, since the fibers in the pattern portions are bent, they are non-linear, that is, their orientations vary from their tips down to the surface of the adhesive layer in which they are retained and their appearance is thereby affected in a manner which may be undesirable.
In another prior system the pattern is impressed on the fibers before the binding adhesive has set or cured. Again the flocked material is passed beneath a cylinder. This time, the cylinder is provided with apertures corresponding to the desired pattern. A cylindrical brush fills the interior of the cylinder and the bristles of this brush extend into the apertures, essentially flush with the external surface of the cylinder. The cylinder rotates with the moving material at the same speed as the material, while the brush rotates within the cylinder in the same direction but at a considerably higher speed. As a result, the fibers contacted by the cylinder surface are tilted in a direction opposite the direction of movement of the material, while those contacted by the brush are tilted in the direction of material movement, thereby forming the desired pattern. Subsequent curing of the adhesive retains the fibers in their differentially tilted orientations. This arrangement has the advantage of superior appearance since the fibers are linear, i.e., they have the same orientations throughout their lengths. However, proper operation of the system requires the use of a very thin cylinder, which is difficult to manufacture and also is difficult to support so as to maintain its desired cylindrical shape. Moreover, with this system it is difficult to impress patterns having fine detail.
Another prior system operating on the fibers before the adhesive has set employs an apertured cylinder. Air jets passing through the apertures tilt the fibers on which they impinge, thus forming the desired pattern. This system too provides a superior appearance to the fibers which are thereby tilted rather than bent. However, it is incapable of providing patterns with sharp edges and fine detail.